In a conventional gas fired water heater, the gas burner is located beneath the lower head of the tank and waste gases of combustion from the burner pass upwardly through one or more flues that extend through the tank. With this construction, heat is transferred from the lower burner through the head to the water in the tank, as well as from the waste gases passing through the flues to the water.
In an attempt to increase the efficiency of the water heater, heaters have been constructed with an enclosed combustion chamber that is located within the lower portion of the tank in direct contact with the water. With this type of heater, waste gases from the combustion chamber are passed through a heat exchanger also located within the tank, so that additional heat from the waste gases is transferred to the water. Cooling of the waste gases through heat transfer generates substantial quantities of condensate, and in the typical submerged chamber water heater, the condensate is delivered to a collector and is discharged through a condensate trap.
In order to improve the efficiency of operation, it is desired to create turbulence within the heat exchanger tubes, for turbulence increases the rate of heat transfer, and correspondingly increases the rate of condensation of water vapor. As condensation is a heat generating process, the heat produced through condensation can be utilized to further increase the efficiency of operation.
To create turbulence in heat exchanger tubes, various forms of baffles or turbulators have been utilized. The baffles or turbulators should not only increase turbulence, but they should not produce undesirable back pressure and must be able to withstand severe environmental conditions. For example, at the inlet end of the heat exchanger tubes, the temperature of the waste gases may be in the range of about 1300.degree. F. and the gases are dry. However, at the downstream end of the heat exchanger tubes the temperature is substantially lower, but the turbulators are subjected to acidic condensate. Thus, the turbulators must be able to withstand high elevated dry temperatures, as well as acidic environments.
As a further requirement, the turbulators should be firmly mounted within the heat exchanger tubes, yet must be removable for maintenance or replacement.